Cyclopentyl purine derivatives are compounds useful in gene cloning and are known to possess antiviral activity against DNA viruses or RNA viruses. European Patent Application 236935 teaches certain cyclopentyl derivatives as having antiviral activity against DNA viruses (e.g. herpes simplex virus type I or II, cytomegalovirus, Epstein-Barr virus), Hepatitis B virus; or RNA viruses such as human immunodeficiency virus (HIV) which is a pathogen of acquired immunodeficiency syndrome (AIDS), vesicular stomatitis virus, feline leukemia virus and equine infectious anemic virus.
European Patent Application 219838 discloses analogues of cyclopentyl purine derivatives.
A review paper by Victor E. Marquez and Mu-Ill Lim (1986) Medicinal Research Reviews, Vol. 6, No. 1, pages 1-40 by John Wiley & Sims, Inc. teaches numerous cyclopentyl derivatives as well as methods for their preparation.
Although functional, the processes taught for preparing the cyclopentyl purine derivatives of European Patent Application 236935 have the disadvantage of requiring numerous reaction steps. Further, in some of the reaction steps, intermediates must be individually purified before further reaction, requiring even further steps for preparation. Also, in numerous processes protecting groups must be utilized in order to carry out the process. It would be desirable to employ a process for preparing cyclopentyl purine derivatives which requires as few or even fewer steps than other processes previously taught. It would also be desirable to employ a process which can utilize intermediates which can be readily used for further reaction with little or no purification. It would also be desirable to provide intermediates which can be used in such a process. Further, it would be desirable to employ a process which does not require the use of protecting groups in order to carry out the process. It would also be desirable to carry out a process for preparing the cyclopentyl purine derivatives using natural starting materials.